Load a single Mesh node on initial scene construction (the EAGER path).
Returns the placeholder once data has been committed (or empty when no triangles
are currently visible — the slice-update path will populate it later). Throws
LoaderError on failure so loadLeafNode can dispatch by kind and keep the rest
of the scene alive.
Load a single Mesh node on initial scene construction (the EAGER path).
Returns the placeholder once data has been committed (or empty when no triangles are currently visible — the slice-update path will populate it later). Throws
LoaderErroron failure soloadLeafNodecan dispatch by kind and keep the rest of the scene alive.